Challenge Security 1 out of 6 fails. Don't see it

Question

sequence = input("")
sequence.strip("x")

if(sequence.find("$T") ==-1 and sequence.find("T

Answer 1

Hello, thank you.
I tried replace before which didn't work either.
Now I found it. Replace is only part of the solution. I need to write the result back into a new variable, replace doesn't alter the original variable.

Answer 2

Strip removes characters from the left and right part of the string, not in the middle
Use sequence.replace("x", "")